Direct upload with server-side signature and callback

Linux

1. Run the following commands to append the environment variable settings to the ~/.bashrc file.

   echo "export OSS_ACCESS_KEY_ID='your-access-key-id'" >> ~/.bashrc
   echo "export OSS_ACCESS_KEY_SECRET='your-access-key-secret'" >> ~/.bashrc
   echo "export OSS_STS_ROLE_ARN='your-role-arn'" >> ~/.bashrc

2. Run the following command to apply the changes.

   source  ~/.bashrc

3. Run the following commands to check if the environment variables are set.

   echo $OSS_ACCESS_KEY_ID
   echo $OSS_ACCESS_KEY_SECRET
   echo $OSS_STS_ROLE_ARN

macOS

1. Run the following command in the terminal to check the default shell type.

   echo $SHELL

2. Follow the steps for your default shell type.

   Zsh

   1. Run the following commands to append the environment variable settings to the ~/.zshrc file.

      echo "export OSS_ACCESS_KEY_ID='your-access-key-id'" >> ~/.zshrc
      echo "export OSS_ACCESS_KEY_SECRET='your-access-key-secret'" >> ~/.zshrc
      echo "export OSS_STS_ROLE_ARN='your-role-arn'" >> ~/.zshrc

   2. Run the following command to apply the changes.

      source ~/.zshrc

   3. Run the following commands to check if the environment variables are set.

      echo $OSS_ACCESS_KEY_ID
      echo $OSS_ACCESS_KEY_SECRET
      echo $OSS_STS_ROLE_ARN

   Bash

   1. Run the following commands to append the environment variable settings to the ~/.bash_profile file.

      echo "export OSS_ACCESS_KEY_ID='your-access-key-id'" >> ~/.bash_profile
      echo "export OSS_ACCESS_KEY_SECRET='your-access-key-secret'" >> ~/.bash_profile
      echo "export OSS_STS_ROLE_ARN='your-role-arn'" >> ~/.bash_profile

   2. Run the following command to apply the changes.

      source ~/.bash_profile

   3. Run the following commands to check if the environment variables are set.

      echo $OSS_ACCESS_KEY_ID
      echo $OSS_ACCESS_KEY_SECRET
      echo $OSS_STS_ROLE_ARN

Windows

1. Run the following commands in Command Prompt.

   setx OSS_ACCESS_KEY_ID "your-access-key-id"
   setx OSS_ACCESS_KEY_SECRET "your-access-key-secret"
   setx OSS_STS_ROLE_ARN "your-role-arn"

2. Open a new Command Prompt window.

3. In the new Command Prompt window, run the following commands to check if the environment variables are set.

   echo %OSS_ACCESS_KEY_ID%
   echo %OSS_ACCESS_KEY_SECRET%
   echo %OSS_STS_ROLE_ARN%

Java

In your Maven project, add the following dependencies.

<!-- https://mvnrepository.com/artifact/com.aliyun/credentials-java -->
<dependency>
    <groupId>com.aliyun.oss</groupId>
    <artifactId>aliyun-sdk-oss</artifactId>
    <version>3.17.4</version>
</dependency>
<dependency>
  <groupId>com.aliyun</groupId>
  <artifactId>sts20150401</artifactId>
  <version>1.1.6</version>
</dependency>

Use the following sample code to obtain temporary access credentials on the server, calculate a POST signature, and set up an upload callback.

package com.aliyun.oss.web;
import com.aliyun.sts20150401.models.AssumeRoleResponse;
import com.aliyun.sts20150401.models.AssumeRoleResponseBody;
import com.aliyun.tea.TeaException;
import com.aliyun.oss.common.utils.BinaryUtil;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.commons.codec.binary.Base64;
import org.codehaus.jettison.json.JSONObject;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.time.*;
import java.time.format.DateTimeFormatter;
import java.util.*;
@Controller
public class WebController {
    // Basic OSS information. Replace the bucket name, region ID, and host with your actual values.
    String bucket = "examplebucket";
    String region = "cn-hangzhou";
    String host = "http://examplebucket.oss-cn-hangzhou.aliyuncs.com";
    // The URL for the upload callback. This must be a public URL. It is used for communication between your application server and OSS. After a file is uploaded, OSS sends the upload information to your application server through this URL.
    String callbackUrl = "http://oss-demo.aliyuncs.com:23450/callback"; // The URL of the server that receives callback requests. Example: http://oss-demo.aliyuncs.com:23450/callback.
    // The prefix for files uploaded to OSS.
    String upload_dir = "dir";
    // The expiration time in seconds.
    Long expire_time = 3600L;
    /**
     * Generates an expiration time based on a specified duration in seconds.
     * @param seconds The duration in seconds.
     * @return An ISO 8601 time string, for example, "2014-12-01T12:00:00.000Z".
     */
    public static String generateExpiration(long seconds) {
        long now = Instant.now().getEpochSecond();
        long expirationTime = now + seconds;
        Instant instant = Instant.ofEpochSecond(expirationTime);
        ZoneId zone = ZoneOffset.UTC;
        ZonedDateTime zonedDateTime = instant.atZone(zone);
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
        String formattedDate = zonedDateTime.format(formatter);
        return formattedDate;
    }
    // Initializes the STS client.
    public static com.aliyun.sts20150401.Client createStsClient() throws Exception {
        // Leaking your project code can expose your AccessKey pair, compromising the security of all resources under your account. The following sample code is for reference only.
        // We recommend using the more secure STS method.
        com.aliyun.teaopenapi.models.Config config = new com.aliyun.teaopenapi.models.Config()
                // Required. Ensure that the OSS_ACCESS_KEY_ID environment variable is set in your execution environment.
                .setAccessKeyId(System.getenv("OSS_ACCESS_KEY_ID"))
                // Required. Ensure that the OSS_ACCESS_KEY_SECRET environment variable is set in your execution environment.
                .setAccessKeySecret(System.getenv("OSS_ACCESS_KEY_SECRET"));
        // For more information about endpoints, see https://api.aliyun.com/product/Sts
        config.endpoint = "sts.cn-hangzhou.aliyuncs.com";
        return new com.aliyun.sts20150401.Client(config);
    }
    // Obtains temporary credentials from STS.
    public static AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials getCredential() throws Exception {
        com.aliyun.sts20150401.Client client = WebController.createStsClient();
        com.aliyun.sts20150401.models.AssumeRoleRequest assumeRoleRequest = new com.aliyun.sts20150401.models.AssumeRoleRequest()
                // Required. Ensure that the OSS_STS_ROLE_ARN environment variable is set in your execution environment.
                .setRoleArn(System.getenv("OSS_STS_ROLE_ARN"))
                .setRoleSessionName("yourRoleSessionName");// A custom session name.
        com.aliyun.teautil.models.RuntimeOptions runtime = new com.aliyun.teautil.models.RuntimeOptions();
        try {
            // When running this code, print the API return value for debugging.
            AssumeRoleResponse response = client.assumeRoleWithOptions(assumeRoleRequest, runtime);
            // The `credentials` object contains the AccessKeyId, AccessKeySecret, and SecurityToken.
            return response.body.credentials;
        } catch (TeaException error) {
            // This is for demonstration purposes only. Handle exceptions with caution and do not ignore them in your project.
            System.out.println(error.getMessage());
            System.out.println(error.getData().get("Recommend"));
            com.aliyun.teautil.Common.assertAsString(error.message);
        } 
        // Returns a default error response object to avoid returning null.
        AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials defaultCredentials = new AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials();
        defaultCredentials.accessKeyId = "ERROR_ACCESS_KEY_ID";
        defaultCredentials.accessKeySecret = "ERROR_ACCESS_KEY_SECRET";
        defaultCredentials.securityToken = "ERROR_SECURITY_TOKEN";
        return defaultCredentials;
    }
    @GetMapping("/get_post_signature_for_oss_upload")
    public ResponseEntity<Map<String, String>> getPostSignatureForOssUpload() throws Exception {
        AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials sts_data = getCredential();
        String accesskeyid =  sts_data.accessKeyId;
        String accesskeysecret =  sts_data.accessKeySecret;
        String securitytoken =  sts_data.securityToken;
        // Get the current date in yyyyMMdd format, used for the x-oss-credential field.
        ZonedDateTime today = ZonedDateTime.now().withZoneSameInstant(java.time.ZoneOffset.UTC);
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
        String date = today.format(formatter);
        // Get x-oss-date.
        ZonedDateTime now = ZonedDateTime.now().withZoneSameInstant(java.time.ZoneOffset.UTC);
        DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss'Z'");
        String x_oss_date = now.format(formatter2);
        // Step 1: Create a policy.
        String x_oss_credential = accesskeyid + "/" + date + "/" + region + "/oss/aliyun_v4_request";
        ObjectMapper mapper = new ObjectMapper();
        Map<String, Object> policy = new HashMap<>();
        policy.put("expiration", generateExpiration(expire_time));
        List<Object> conditions = new ArrayList<>();
        Map<String, String> bucketCondition = new HashMap<>();
        bucketCondition.put("bucket", bucket);
        conditions.add(bucketCondition);
        Map<String, String> securityTokenCondition = new HashMap<>();
        securityTokenCondition.put("x-oss-security-token", securitytoken);
        conditions.add(securityTokenCondition);
        Map<String, String> signatureVersionCondition = new HashMap<>();
        signatureVersionCondition.put("x-oss-signature-version", "OSS4-HMAC-SHA256");
        conditions.add(signatureVersionCondition);
        Map<String, String> credentialCondition = new HashMap<>();
        credentialCondition.put("x-oss-credential", x_oss_credential); // Replace with your actual AccessKey ID.
        conditions.add(credentialCondition);
        Map<String, String> dateCondition = new HashMap<>();
        dateCondition.put("x-oss-date", x_oss_date);
        conditions.add(dateCondition);
        conditions.add(Arrays.asList("content-length-range", 1, 10240000));
        conditions.add(Arrays.asList("eq", "$success_action_status", "200"));
        conditions.add(Arrays.asList("starts-with", "$key", upload_dir));
        policy.put("conditions", conditions);
        String jsonPolicy = mapper.writeValueAsString(policy);
        // Step 2: Construct the string to sign.
        String stringToSign = new String(Base64.encodeBase64(jsonPolicy.getBytes()));
        // Step 3: Calculate the signing key.
        byte[] dateKey = hmacsha256(("aliyun_v4" + accesskeysecret).getBytes(), date);
        byte[] dateRegionKey = hmacsha256(dateKey, region);
        byte[] dateRegionServiceKey = hmacsha256(dateRegionKey, "oss");
        byte[] signingKey = hmacsha256(dateRegionServiceKey, "aliyun_v4_request");
        // Step 4: Calculate the signature.
        byte[] result = hmacsha256(signingKey, stringToSign);
        String signature = BinaryUtil.toHex(result);
        // Step 5: Configure the callback.
        JSONObject jasonCallback = new JSONObject();
        jasonCallback.put("callbackUrl", callbackUrl);
        jasonCallback.put("callbackBody","filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}");
        jasonCallback.put("callbackBodyType", "application/x-www-form-urlencoded");
        String base64CallbackBody = BinaryUtil.toBase64String(jasonCallback.toString().getBytes());
        Map<String, String> response = new HashMap<>();
        // Add data to the map.
        response.put("version", "OSS4-HMAC-SHA256");
        response.put("policy", stringToSign);
        response.put("x_oss_credential", x_oss_credential);
        response.put("x_oss_date", x_oss_date);
        response.put("signature", signature);
        response.put("security_token", securitytoken);
        response.put("dir", upload_dir);
        response.put("host", host);
        response.put("callback", base64CallbackBody);
        // Return a ResponseEntity with status code 200 (OK) to the web client for the PostObject operation.
        return ResponseEntity.ok(response);
    }
    public static byte[] hmacsha256(byte[] key, String data) {
        try {
            // Initializes the HMAC key specification, sets the algorithm to HmacSHA256, and uses the provided key.
            SecretKeySpec secretKeySpec = new SecretKeySpec(key, "HmacSHA256");
            // Obtains a Mac instance and uses the getInstance method to specify the HmacSHA256 algorithm.
            Mac mac = Mac.getInstance("HmacSHA256");
            // Initializes the Mac object with the key.
            mac.init(secretKeySpec);
            // Calculates the HMAC hash of the data.
            byte[] hmacBytes = mac.doFinal(data.getBytes());
            return hmacBytes;
        } catch (Exception e) {
            throw new RuntimeException("Failed to calculate HMAC-SHA256", e);
        }
    }
}

Python

Run the following command to install dependencies.

pip install flask
pip install alibabacloud_tea_openapi alibabacloud_sts20150401 alibabacloud_credentials

Use the following sample code to obtain temporary access credentials from STS, build an upload policy, calculate a POST signature, and set up a callback.

from flask import Flask, render_template, jsonify, request
from alibabacloud_tea_openapi.models import Config
from alibabacloud_sts20150401.client import Client as Sts20150401Client
from alibabacloud_sts20150401 import models as sts_20150401_models
import os
import json
import base64
import hmac
import datetime
import time
import hashlib
import oss2
app = Flask(__name__)
# Configure the OSS_ACCESS_KEY_ID, OSS_ACCESS_KEY_SECRET, and OSS_STS_ROLE_ARN environment variables.
access_key_id = os.environ.get('OSS_ACCESS_KEY_ID')
access_key_secret = os.environ.get('OSS_ACCESS_KEY_SECRET')
role_arn_for_oss_upload = os.environ.get('OSS_STS_ROLE_ARN')
# A custom session name.
role_session_name = 'yourRoleSessionName'
# Replace with the actual bucket name, region ID, and host.
bucket = 'examplebucket'
region_id = 'cn-hangzhou'
host = 'http://examplebucket.oss-cn-hangzhou.aliyuncs.com'
# The expiration time in seconds.
expire_time = 3600
# The prefix for files uploaded to OSS.
upload_dir = 'dir'
def hmacsha256(key, data):
    """
    A function to calculate an HMAC-SHA256 hash value.
    :param key: The key for calculating the hash, in bytes.
    :param data: The data to be hashed, as a string.
    :return: The calculated HMAC-SHA256 hash value, in bytes.
    """
    try:
        mac = hmac.new(key, data.encode(), hashlib.sha256)
        hmacBytes = mac.digest()
        return hmacBytes
    except Exception as e:
        raise RuntimeError(f"Failed to calculate HMAC-SHA256 due to {e}")
@app.route("/")
def hello_world():
    return render_template('index.html')
@app.route('/get_post_signature_for_oss_upload', methods=['GET'])
def generate_upload_params():
    # Initialize the configuration by directly passing the credentials.
    config = Config(
        region_id=region_id,
        access_key_id=access_key_id,
        access_key_secret=access_key_secret
    )
    # Create an STS client and obtain temporary credentials.
    sts_client = Sts20150401Client(config=config)
    assume_role_request = sts_20150401_models.AssumeRoleRequest(
        role_arn=role_arn_for_oss_upload,
        role_session_name=role_session_name
    )
    response = sts_client.assume_role(assume_role_request)
    token_data = response.body.credentials.to_map()
    # Use the temporary credentials returned by STS.
    temp_access_key_id = token_data['AccessKeyId']
    temp_access_key_secret = token_data['AccessKeySecret']
    security_token = token_data['SecurityToken']
    now = int(time.time())
    # Convert the timestamp to a datetime object.
    dt_obj = datetime.datetime.utcfromtimestamp(now)
    # Set the request expiration time to 3 hours from the current time.
    dt_obj_plus_3h = dt_obj + datetime.timedelta(hours=3)
    # Request time.
    dt_obj_1 = dt_obj.strftime('%Y%m%dT%H%M%S') + 'Z'
    # Request date.
    dt_obj_2 = dt_obj.strftime('%Y%m%d')
    # Request expiration time.
    expiration_time = dt_obj_plus_3h.strftime('%Y-%m-%dT%H:%M:%S.000Z')
    # Define a function to Base64-encode the callback parameters.
    def encode_callback(callback_params):
        cb_str = json.dumps(callback_params).strip()
        return oss2.compat.to_string(base64.b64encode(oss2.compat.to_bytes(cb_str)))
    # Build the callback configuration and Base64-encode it.
    callback_config = {
        "callbackUrl": "http://oss-demo.aliyuncs.com:23450/callback",  # The URL of your callback server.
        "callbackBody": "bucket=${bucket}&object=${object}&etag=${etag}&size=${size}",
        "callbackBodyType": "application/x-www-form-urlencoded"
    }
    encoded_callback = encode_callback(callback_config)
    # Build the policy and generate the signature.
    policy = {
        "expiration": expiration_time,
        "conditions": [
            ["eq", "$success_action_status", "200"],
            {"x-oss-signature-version": "OSS4-HMAC-SHA256"},
            {"x-oss-credential": f"{temp_access_key_id}/{dt_obj_2}/cn-hangzhou/oss/aliyun_v4_request"},
            {"x-oss-security-token": security_token},
            {"x-oss-date": dt_obj_1},
        ]
    }
    policy_str = json.dumps(policy).strip()
    # Step 2: Construct the string to sign.
    stringToSign = base64.b64encode(policy_str.encode()).decode()
    # Step 3: Calculate the signing key.
    dateKey = hmacsha256(("aliyun_v4" + temp_access_key_secret).encode(), dt_obj_2)
    dateRegionKey = hmacsha256(dateKey, "cn-hangzhou")
    dateRegionServiceKey = hmacsha256(dateRegionKey, "oss")
    signingKey = hmacsha256(dateRegionServiceKey, "aliyun_v4_request")
    # Step 4: Calculate the signature.
    result = hmacsha256(signingKey, stringToSign)
    signature = result.hex()
    # Prepare the response data.
    response_data = {
        'policy': stringToSign,  # The form field.
        'x_oss_signature_version': "OSS4-HMAC-SHA256",  # The signature version and algorithm. The value is fixed at OSS4-HMAC-SHA256.
        'x_oss_credential': f"{temp_access_key_id}/{dt_obj_2}/cn-hangzhou/oss/aliyun_v4_request",  # The parameter set that specifies the derived key.
        'x_oss_date': dt_obj_1,  # The request time.
        'signature': signature,  # The signature information.
        'host': host,
        'dir': upload_dir,
        'security_token': security_token,  # The security token.
        'callback': encoded_callback   # The Base64-encoded callback configuration.
    }
    return jsonify(response_data)
if __name__ == "__main__":
    app.run(host="127.0.0.1", port=8000)  # If you need to listen on other addresses, such as 0.0.0.0, you must add an authentication mechanism on the server.

Node.js

Run the following command to install dependencies.

npm install ali-oss
npm install @alicloud/credentials
npm install express

Use the following sample code to obtain temporary access credentials from STS, build an upload policy, calculate a POST signature, and set up a callback.

const express = require('express');
const OSS = require('ali-oss');
const { STS } = require('ali-oss');
const { getCredential } = require('ali-oss/lib/common/signUtils');
const { getStandardRegion } = require('ali-oss/lib/common/utils/getStandardRegion');
const { policy2Str } = require('ali-oss/lib/common/utils/policy2Str');
const app = express();
const PORT = process.env.PORT || 8000; // The service request port.
// Set the static file directory.
app.use(express.static('templates'));
const GenerateSignature = async () => {
    // Initialize the STS client.
    let sts = new STS({
        accessKeyId: process.env.OSS_ACCESS_KEY_ID,  // Obtain the AccessKey ID of the RAM user from environment variables.
        accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET // Obtain the AccessKey secret of the RAM user from environment variables.
    });
    // Call the assumeRole operation to obtain temporary access credentials from STS.
    const result = await sts.assumeRole(process.env.OSS_STS_ROLE_ARN, '', '3600', 'yourRoleSessionName'); // Obtain the RAM role ARN from an environment variable, set the validity period of the temporary access credentials to 3,600 seconds, and specify a custom role session name.
    // Extract the AccessKeyId, AccessKeySecret, and SecurityToken from the temporary access credentials.
    const accessKeyId = result.credentials.AccessKeyId;
    const accessKeySecret = result.credentials.AccessKeySecret;
    const securityToken = result.credentials.SecurityToken;
    // Initialize the OSS client.
    const client = new OSS({
        bucket: 'examplebucket', // Replace with your target bucket name.
        region: 'cn-hangzhou', // Replace with the region of your target bucket.
        accessKeyId,
        accessKeySecret,
        stsToken: securityToken,
        refreshSTSTokenInterval: 0,
        refreshSTSToken: async () => {
            const { accessKeyId, accessKeySecret, securityToken } = await client.getCredential();
            return { accessKeyId, accessKeySecret, stsToken: securityToken };
        },
    });
    // Create a form data Map.
    const formData = new Map();
    // Set the signature expiration time to 10 minutes from the current time. 
    const date = new Date();
    const expirationDate = new Date(date);
    expirationDate.setMinutes(date.getMinutes() + 10);
    // Format the date to a UTC time string compliant with the ISO 8601 standard.
    function padTo2Digits(num) {
        return num.toString().padStart(2, '0');
    }
    function formatDateToUTC(date) {
        return (
            date.getUTCFullYear() +
            padTo2Digits(date.getUTCMonth() + 1) +
            padTo2Digits(date.getUTCDate()) +
            'T' +
            padTo2Digits(date.getUTCHours()) +
            padTo2Digits(date.getUTCMinutes()) +
            padTo2Digits(date.getUTCSeconds()) +
            'Z'
        );
    }
    const formattedDate = formatDateToUTC(expirationDate);
    // The URL for the upload callback. This is used for communication between your application server and OSS. After a file is uploaded, OSS sends the upload information to your application server through this URL. For example, set callbackUrl to https://oss-demo.aliyuncs.com:23450.
    // Generate x-oss-credential and set the form data.
    const credential = getCredential(formattedDate.split('T')[0], getStandardRegion(client.options.region), client.options.accessKeyId);
    formData.set('x_oss_date', formattedDate);
    formData.set('x_oss_credential', credential);
    formData.set('x_oss_signature_version', 'OSS4-HMAC-SHA256');
    // Create a policy.
    // The following policy contains the minimum required fields.
    const policy = {
        expiration: expirationDate.toISOString(),
        conditions: [
            { 'bucket': 'examplebucket' }, // Replace with your target bucket name.
            { 'x-oss-credential': credential },
            { 'x-oss-signature-version': 'OSS4-HMAC-SHA256' },
            { 'x-oss-date': formattedDate },
        ],
    };
    // If an STS token exists, add it to the policy and form data.
    if (client.options.stsToken) {
        policy.conditions.push({ 'x-oss-security-token': client.options.stsToken });
        formData.set('security_token', client.options.stsToken);
    }
    // Generate the signature and set the form data.
    const signature = client.signPostObjectPolicyV4(policy, date);
    formData.set('policy', Buffer.from(policy2Str(policy), 'utf8').toString('base64'));
    formData.set('signature', signature);
    const callback = {
      callbackUrl: 'http://oss-demo.aliyuncs.com:23450/callback',// The URL of the server that receives callback requests. Example: http://oss-demo.aliyuncs.com:23450/callback.
      callbackBody:// The content of the callback, such as the file ETag and resource MIME type.
      "filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}",
      callbackBodyType: "application/x-www-form-urlencoded",// The content type of the callback.    
    };
    // Return the form data.
    return {
        host: `http://${client.options.bucket}.oss-${client.options.region}.aliyuncs.com`, 
        policy: Buffer.from(policy2Str(policy), 'utf8').toString('base64'),
        x_oss_signature_version: 'OSS4-HMAC-SHA256',
        x_oss_credential: credential,
        x_oss_date: formattedDate,
        signature: signature,
        dir: 'user-dir', // The prefix for files uploaded to OSS.
        callback: Buffer.from(JSON.stringify(callback)).toString("base64"),// Base64-encode the JSON object by using Buffer.from.
        security_token: client.options.stsToken
    };
};
app.get('/get_post_signature_for_oss_upload', async (req, res) => {
    try {
        const result = await GenerateSignature();
        res.json(result); // Return the generated signature data.
    } catch (error) {
        console.error('Error generating signature:', error);
        res.status(500).send('Error generating signature');
    }
});
app.listen(PORT, () => {
    console.log(`Server is running on http://127.0.0.1:${PORT}`); // If you need to listen on other addresses, such as 0.0.0.0, you must add an authentication mechanism on the server.
});

Go

Run the following command to install dependencies.

go get -u github.com/aliyun/credentials-go
go mod tidy

Use the following sample code to obtain temporary access credentials from STS, build an upload policy, calculate a POST signature, and set up a callback.

package main
import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
    "hash"
	"log"
	"net/http"
	"os"
	"time"
	"github.com/aliyun/credentials-go/credentials"
)
// Define global variables.
var (
	region     string
	bucketName string
	product    = "oss"
)
// The PolicyToken struct is used to store the generated form data.
type PolicyToken struct {
	Policy           string `json:"policy"`
	SecurityToken    string `json:"security_token"`
	SignatureVersion string `json:"x_oss_signature_version"`
	Credential       string `json:"x_oss_credential"`
	Date             string `json:"x_oss_date"`
	Signature        string `json:"signature"`
	Host             string `json:"host"` 
	Dir              string `json:"dir"` 
    Callback         string `json:"callback"`
}
type CallbackParam struct{
    CallbackUrl string `json:"callbackUrl"`
    CallbackBody string `json:"callbackBody"`
    CallbackBodyType string `json:"callbackBodyType"`
}
func main() {
	// Define the default IP address and port string.
	strIPPort := ":8080"
	if len(os.Args) == 3 {
		strIPPort = fmt.Sprintf("%s:%s", os.Args[1], os.Args[2])
	} else if len(os.Args) != 1 {
		fmt.Println("Usage   : go run test1.go                ")
		fmt.Println("Usage   : go run test1.go ip port        ")
		fmt.Println("Example : go run test1.go 11.22.**.** 80 ")
		fmt.Println("Example : go run test1.go 0.0.0.0 8080 ")
		fmt.Println("")
		os.Exit(0)
	}
	// Print the address and port where the server is running.
	fmt.Printf("server is running on %s \n", strIPPort)
	// Register the function to handle requests for the root path.
	http.HandleFunc("/", handlerRequest)
	// Register the function to handle requests for obtaining signatures.
	http.HandleFunc("/get_post_signature_for_oss_upload", handleGetPostSignature)
	// Start the HTTP server.
	err := http.ListenAndServe(strIPPort, nil)
	if err != nil {
		strError := fmt.Sprintf("http.ListenAndServe failed : %s \n", err.Error())
		panic(strError)
	}
}
// The handlerRequest function handles requests for the root path.
func handlerRequest(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		http.ServeFile(w, r, "templates/index.html")
		return
	}
	http.NotFound(w, r)
}
// The handleGetPostSignature function handles requests for obtaining signatures.
func handleGetPostSignature(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		response := getPolicyToken()
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Access-Control-Allow-Origin", "*") // Allow cross-origin requests.
		w.Write([]byte(response))
		return
	}
	http.NotFound(w, r)
}
// The getPolicyToken function generates the signature and credentials required for OSS uploads.
func getPolicyToken() string {
	// Set the region where the bucket is located.
	region = "cn-hangzhou"
	// Set the bucket name.
	bucketName = "examplebucket"
	// Set the OSS upload endpoint.
	host := fmt.Sprintf("https://%s.oss-%s.aliyuncs.com", bucketName, region)
	// Set the upload directory.
	dir := "user-dir"
    // callbackUrl is the URL of the server that receives upload callbacks. Replace the IP address and port with your actual information.
    callbackUrl := "http://oss-demo.aliyuncs.com:23450/callback";
	config := new(credentials.Config).
		SetType("ram_role_arn").
		SetAccessKeyId(os.Getenv("OSS_ACCESS_KEY_ID")).
		SetAccessKeySecret(os.Getenv("OSS_ACCESS_KEY_SECRET")).
		SetRoleArn(os.Getenv("OSS_STS_ROLE_ARN")).
		SetRoleSessionName("Role_Session_Name").
		SetPolicy("").
		SetRoleSessionExpiration(3600)
	// Create a credential provider based on the configuration.
	provider, err := credentials.NewCredential(config)
	if err != nil {
		log.Fatalf("NewCredential fail, err:%v", err)
	}
	// Obtain credentials from the credential provider.
	cred, err := provider.GetCredential()
	if err != nil {
		log.Fatalf("GetCredential fail, err:%v", err)
	}
	// Build the policy.
	utcTime := time.Now().UTC()
	date := utcTime.Format("20060102")
	expiration := utcTime.Add(1 * time.Hour)
	policyMap := map[string]any{
		"expiration": expiration.Format("2006-01-02T15:04:05.000Z"),
		"conditions": []any{
			map[string]string{"bucket": bucketName},
			map[string]string{"x-oss-signature-version": "OSS4-HMAC-SHA256"},
			map[string]string{"x-oss-credential": fmt.Sprintf("%v/%v/%v/%v/aliyun_v4_request", *cred.AccessKeyId, date, region, product)},
			map[string]string{"x-oss-date": utcTime.Format("20060102T150405Z")},
			map[string]string{"x-oss-security-token": *cred.SecurityToken},
		},
	}
	// Convert the policy to JSON format.
	policy, err := json.Marshal(policyMap)
	if err != nil {
		log.Fatalf("json.Marshal fail, err:%v", err)
	}
    // Construct the string to sign.
    stringToSign := base64.StdEncoding.EncodeToString([]byte(policy))
    hmacHash := func() hash.Hash { return sha256.New() }
    // Build the signing key.
    signingKey := "aliyun_v4" + *cred.AccessKeySecret
    h1 := hmac.New(hmacHash, []byte(signingKey))
    io.WriteString(h1, date)
    h1Key := h1.Sum(nil)
    h2 := hmac.New(hmacHash, h1Key)
    io.WriteString(h2, region)
    h2Key := h2.Sum(nil)
    h3 := hmac.New(hmacHash, h2Key)
    io.WriteString(h3, product)
    h3Key := h3.Sum(nil)
    h4 := hmac.New(hmacHash, h3Key)
    io.WriteString(h4, "aliyun_v4_request")
    h4Key := h4.Sum(nil)
    // Generate the signature.
    h := hmac.New(hmacHash, h4Key)
    io.WriteString(h, stringToSign)
    signature := hex.EncodeToString(h.Sum(nil))
    var callbackParam CallbackParam
    callbackParam.CallbackUrl = callbackUrl
    callbackParam.CallbackBody = "filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}"
    callbackParam.CallbackBodyType = "application/x-www-form-urlencoded"
    callback_str,err:=json.Marshal(callbackParam)
    if err != nil {
        fmt.Println("callback json err:", err)
    }
    callbackBase64 := base64.StdEncoding.EncodeToString(callback_str)
	// Build the form to be returned to the client.
	policyToken := PolicyToken{
		Policy:           stringToSign,
		SecurityToken:    *cred.SecurityToken,
		SignatureVersion: "OSS4-HMAC-SHA256",
		Credential:       fmt.Sprintf("%v/%v/%v/%v/aliyun_v4_request", *cred.AccessKeyId, date, region, product),
		Date:             utcTime.UTC().Format("20060102T150405Z"),
		Signature:        signature,
		Host:             host, // The OSS upload endpoint.
		Dir:              dir,  // The upload directory.
        Callback:         callbackBase64, // The upload callback parameters.
	}
	response, err := json.Marshal(policyToken)
	if err != nil {
		fmt.Println("json err:", err)
	}
	return string(response)
}

PHP

Run the following command to install dependencies.

composer install

Use the following sample code to obtain temporary access credentials from STS, build an upload policy, calculate a POST signature, and set up a callback.

<?php
// Import the Alibaba Cloud SDK.
require_once __DIR__ . '/vendor/autoload.php';
use AlibabaCloud\Client\AlibabaCloud;
use AlibabaCloud\Client\Exception\ClientException;
use AlibabaCloud\Client\Exception\ServerException;
use AlibabaCloud\Sts\Sts;
// Disable error display.
ini_set('display_errors', '0');
$bucket = 'examplebucket'; // Replace with your bucket name.
$region_id = 'cn-hangzhou'; // Replace with the region of your bucket.
$host = 'http://examplebucket.oss-cn-hangzhou.aliyuncs.com'; // Replace with your bucket domain name.
$expire_time = 3600; // Expiration time in seconds.
$upload_dir = 'user-dir'; // Prefix for uploaded files.
// $callbackUrl is the URL of the server that receives upload callbacks. Replace the IP address and port with your actual URL.
$callbackUrl = 'http://oss-demo.aliyuncs.com:23450/callback';
// Calculate HMAC-SHA256.
function hmacsha256($key, $data) {
    return hash_hmac('sha256', $data, $key, true);
}
// Handle the request to obtain the POST signature.
if ($_SERVER['REQUEST_METHOD'] === 'GET' && $_SERVER['REQUEST_URI'] === '/get_post_signature_for_oss_upload') {
    AlibabaCloud::accessKeyClient(getenv('OSS_ACCESS_KEY_ID'), getenv('OSS_ACCESS_KEY_SECRET'))
        ->regionId('cn-hangzhou')
        ->asDefaultClient();
    // Create an STS request.
    $request = Sts::v20150401()->assumeRole();
    // Initiate the STS request and obtain the result.
    // Set  to a custom session name, for example, oss-role-session.
    // Replace  with the ARN of a RAM role that has permissions to upload files to the specified OSS bucket.
    $result = $request
        ->withRoleSessionName('oss-role-session')
        ->withDurationSeconds(3600)
        ->withRoleArn(getenv('OSS_STS_ROLE_ARN')) // Replace with your RAM role ARN.
        ->request();
    // Obtain the credential information from the STS request result.
    $tokenData = $result->get('Credentials');
    // Build the returned JSON data.
    $tempAccessKeyId = $tokenData['AccessKeyId'];
    $tempAccessKeySecret = $tokenData['AccessKeySecret'];
    $securityToken = $tokenData['SecurityToken'];
    $now = time();
    $dtObj = gmdate('Ymd\THis\Z', $now);
    $dtObj1 = gmdate('Ymd', $now);
    $dtObjPlus3h = gmdate('Y-m-d\TH:i:s.u\Z', strtotime('+3 hours', $now));
    // Build the policy.
    $policy = [
        "expiration" => $dtObjPlus3h,
        "conditions" => [
            ["x-oss-signature-version" => "OSS4-HMAC-SHA256"],
            ["x-oss-credential" => "{$tempAccessKeyId}/{$dtObj1}/cn-hangzhou/oss/aliyun_v4_request"],
            ["x-oss-security-token" => $securityToken],
            ["x-oss-date" => $dtObj],
        ]
    ];
    $policyStr = json_encode($policy);
    // Construct the string to sign.
    $stringToSign = base64_encode($policyStr);
    // Calculate the signing key.
    $dateKey = hmacsha256(('aliyun_v4' . $tempAccessKeySecret), $dtObj1);
    $dateRegionKey = hmacsha256($dateKey, 'cn-hangzhou');
    $dateRegionServiceKey = hmacsha256($dateRegionKey, 'oss');
    $signingKey = hmacsha256($dateRegionServiceKey, 'aliyun_v4_request');
    // Calculate the signature.
    $result = hmacsha256($signingKey, $stringToSign);
    $signature = bin2hex($result);
    $callback_param = array(
    'callbackUrl' => $callbackUrl,
    'callbackBody' => 'filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}',
    'callbackBodyType' => "application/x-www-form-urlencoded"
    );
    $callback_string = json_encode($callback_param);
    $base64_callback_body = base64_encode($callback_string);
    // Return the signature data.
    $responseData = [
        'policy' => $stringToSign,
        'x_oss_signature_version' => "OSS4-HMAC-SHA256",
        'x_oss_credential' => "{$tempAccessKeyId}/{$dtObj1}/cn-hangzhou/oss/aliyun_v4_request",
        'x_oss_date' => $dtObj,
        'signature' => $signature,
        'host' => $host,
        'dir' => $upload_dir,
        'security_token' => $securityToken,
        'callback' => $base64_callback_body,
    ];
    header('Content-Type: application/json');
    echo json_encode($responseData);
    exit;
}
// Homepage route.
if ($_SERVER['REQUEST_METHOD'] === 'GET' && $_SERVER['REQUEST_URI'] === '/') {
    echo file_get_contents(__DIR__ . '/public/index.html');
    exit;
}
// Other routes.
http_response_code(404);
echo json_encode(['message' => 'Not Found']);
exit;
?>